<del>I have found a workaround:
change capability in add_submenu_page('upload.php', __("Replace media", "enable-media-replace"), '','upload_files', __FILE__, 'emr_options'); function to anything what noone has, e.g. "xxx"
add_submenu_page('upload.php', __("Replace media", "enable-media-replace"), '','xxx', __FILE__, 'emr_options');
</del> - it works but it than does not show the page after clicking "replace media"
but anyway i think, there is a better way to access the get parameter, e.g. admin_init action, query_vars filter etc.